The cause of myelin damage is still hotly debated: some believe it to be an autoimmune disease while others cite viruses or the environment as the culprit. There is growing evidence however of a correlation between multiple sclerosis and vitamin D deficiency. Epidemiological studies also show that populations closer to the equator and the sun, have far fewer case of multiple sclerosis than populations closer to the north or south poles. Researchers at Oxford University have now taken this premise a step further by showing that vitamin D deficiency and therefore multiple sclerosis could have a genetic cause.